The present invention relates to a method and instruments for resection of the distal femur. In the prior art, instruments are known which are utilized in resecting the distal femur so as to facilitate the installation of a distal femoral prosthesis. In general, the instruments known in the prior art are deficient because they do not enable the determination of the exact location of resection with sufficient accuracy so as to facilitate completely accurate installation of the prosthesis and proper operation of the prosthesis thereafter. The prior art includes the use of flexible cords in measuring and determining resection angles and such devices are inherently faulty as being required to be maintained in a stretched orientation at all times to maintain accuracy. Furthermore, the prior art teaches the use of alignment rods. However, no alignment rod is known to Applicant which includes the feature of being pivotably attached to a plate insertable into a slot which is intended for use as a guide with the resection tool. Thus, the interaction between the slot and the plate as well as the rod pivotably attached to the plate so as to ensure accurate resection of the distal femur perpendicular to the mechanical axis of the leg is nowhere taught in the prior art.
The following prior art is known to Applicant:
U.S. Pat. No. 4,179,810 to Kirsch discloses a device for milling slots in a jawbone for mounting an endossal device. The milling device includes a circular sawblade in a two-part housing with one part carrying the blade and the other forming a guide. Of course, guide slots for the resection of bones are well known in the art, and the present invention has significant advantages over the teacings of Kirsch when used in the environment of the resection of the distal femur such as, for example, the interaction of the guide slot on the resector with the pivotable elongated guide rod which ensures alignment of the resection in a prescribed way with respect to the mechanical axis of the leg.
U.S. Pat. No. 4,325,373 to Slavanko, et al. discloses an apparatus for forming an osteotomy for a dental implant which includes a drill guide for forming a precise elongated slot with the drill guide having pins which fit into drilled guide holes to accurately position the guide means. Of course, it is well known in the prior art to utilize pins to fasten a guiding device onto a bone which is to be resected. The present invention teaches a combination of elements nowhere found in Slavanko, et al.
U.S. Pat. No. 4,349,018 to Chambers discloses an osteotomy apparatus for use in guiding and aligning a cutting means for bone removal from the tibia and femur during knee replacement. The apparatus utilizes T bar units connected to the femur and tibia which provide support for cutting guide members that are selectively positionable for total knee replacement or proximal tibia osteotomy. Of course, the present invention is vastly different from the teachings of Chambers as including, for example, a rotating rod on the resector which enables the placement of pins in such a way that the resector will be perfectly aligned and engaged with a filed plane on the anterior femoral cortex.
U.S. Pat. No. 4,457,307 to Stillwell discloses a bone cutting device for total knee replacement which includes a femoral attached assembly and a carriage assembly connected and pivotably adjustable with respect thereto. A saw carriage on the assembly supports a powered saw for making the necessary cuts.
The present invention is much simpler than Stillwell and is more concerned with the specifics of perfectly aligning a guide slot in the resector with the appropriate area on the distal femur. Stillwell is more concerned with a guiding device for guiding the movements of a saw in its associated carriage.
U.S. Pat. No. 4,487,203 to Androphy discloses a tri-planar knee resection method utilizing a single guide member selectively positionable on guide rods for performing all the necessary cuts to the distal femur or proximal tibia. The present invention is much simpler than Androphy and does not include means for performing cuts on the proximal tibia. Rather, the present invention relates to an invention which is designed for a very specific purpose, namely, the resection of the distal femur and is specifically designed so as to achieve distal femoral resection with the greatest possible accuracy.
U.S. Pat. No. 4,502,483 to Lacey discloses a method and apparatus for shaping a distal femoral surface which employs an alignment guide comprising a main body, a pivotable resection guide instrument holder, a locator pin and a femoral surface modifying instrument. A clamp is provided for affixing the main body to the femur and the locator pin is used to align the axis of the main body with the axis of the femur. While this device is generally related to the present invention, the present invention is believed to clearly distinguish therefrom since in the present invention the resector may be aligned with the mechanical axis of the body through the use of a guide/rod which is pivotable to a position wherein it may be aligned with the mechanical axis of the leg and having attached thereto a plate which may be inserted into the precise slot in the resector through which the cutting device will be inserted for the purpose of resecting the distal femur.
Further, U.S. design Pat. Nos. 272,854 to Witte, et al. and 274,162 to Kenna are also known to applicant and are believed to be only of general interest concerning the teachings of the present invention.